Republican U.S. presidential candidate Rick Santorum prays with members of his campaign staff during lunch between stops in Le Mars, Iowa on October 30, 2015.

A young woman takes a photo of the stage design after Republican U.S. presidential candidate Ted Cruz's event with Dr. James Dobson, an evangelical Christian author in Winterset Stage in Winterset, Iowa January 4, 2016.

A supporter of Republican U.S. presidential candidate Donald Trump reaches out for a handshake after a rally in Spencer, Iowa on December 5, 2015.

A member of Democratic U.S. presidential candidate Bernie Sanders' staff awaits his arrival as arrows point his path toward the microphone at an event in a garage in Charles City, Iowa on January 30, 2016.

U.S. Secret Service agents secure the area around the motorcade of Republican U.S. presidential candidate Ben Carson after a campaign even at South Bethel Church in Tipton, Iowa on November 22, 2015.

A flag waves in the wind outside a house down the street from where Democratic U.S. presidential candidate Bernie Sanders was scheduled to speak in Marshalltown, Iowa on January 31, 2016.

Democratic U.S. presidential candidate Maryland Governor Martin O'Malley listens to his introduction as he prepares to speak at the Des Moines County Democrats' fundraiser in Burlington, Iowa on November 7, 2015.

A man adjusts a flag ahead of Republican U.S. presidential candidate Ted Cruz' campaign stop at Godfather's Pizza in Spirit Lake, Iowa on January 6, 2016.

Attendees, including the local sheriff, mingle before Republican U.S. presidential candidate Marco Rubio's town hall event in Pella, Iowa on December 30, 2015.

Laurale Hunter rests her head on the chest of Republican U.S. presidential candidate Ben Carson after he gave a speech about his faith life at South Bethel Church in Tipton, Iowa on November 22, 2015.

Supporters listen as Republican U.S. presidential candidate Ted Cruz does a live television interview ahead of his campaign stop at Prime Time Restaurant in Guthrie Center, Iowa on January 4, 2016.

A member of the New Jersey State Police Executive Protection Unit watches over the crowd as Republican presidential candidate New Jersey Governor Chris Christie greets supporters after a town hall event at Mickey's Irish Pub in Waukee, Iowa on December 30, 2015.

Republican U.S. presidential candidate Ted Cruz does a live television interview with Sean Hannity before a campaign stop at Prime Time Restaurant in Guthrie Center, Iowa on January 4, 2016.

Supporters watch as Democratic U.S. presidential candidate Hillary Clinton speaks during a town hall at Old Brick Church in Iowa City, Iowa on December 16, 2015.

Republican U.S. presidential candidate Donald Trump turns to the crowd behind him during a campaign event in Des Moines, Iowa on Friday, Dec. 11, 2015.

Andy Meyer , Maggie Timboe, Sasha Fetty and Mia Tiric listen to Democratic U.S. presidential candidate Hillary Clinton speak on screen while at a debate watch event in support of Democratic U.S. presidential candidate Bernie Sanders in Des Moines, Iowa on November 14, 2015.

Democratic U.S. presidential candidate Hillary Clinton points to a question in the audience at a campaign event at Clinton Middle School in Clinton, Iowa on November 22, 2015.

Republican U.S. presidential candidate Donald Trump looks out into the crowd for his Iowa campaign manager while speaking press conference at the John Wayne Birthplace and Museum in Winterset, Iowa on January 19, 2016.

Republican presidential candidate Rick Santorum wades through the deep grass while participating in the Col. Bud Day Pheasant Hunt hosted by Congressman Steve King outside of Akron, Iowa on October 31, 2015.

Democratic U.S. presidential candidate Governor Martin O'Malley lunch after speaking at the Hardin County 2016 Chili Spectacular at the Iowa Falls American Legion in Iowa Falls, Iowa on January 10, 2016.

Debra Sage, a supporter of U.S. Republican presidential candidate Ted Cruz, from Grinnell, Iowa listens as Cruz speaks at a campaign stop at a Pizza Ranch restaurant in Newton, Iowa on November 29, 2015.

Protestors carry signs and chant before a campaign event for Republican U.S. presidential candidate Donald Trump at University of Northern Iowa in Cedar Falls, Iowa on January 12, 2016.

The U.S. Secret Service detail for Republican U.S. presidential candidate Donald Trump stands watch as he signs autographs at a campaign event at University of Northern Iowa in Cedar Falls, Iowa on January 12, 2016.

A woman photographs the podium before Democratic U.S. presidential candidate Bernie Sanders' speech a rally on caucus night in Des Moines, Iowa February 1, 2016.

Republican U.S. presidential candidate Donald Trump is seen on TV at the High Life Lounge in Des Moines, Iowa as he participates in the the Republican debate on FOX Business network in Columbia, South Carolina on January 14, 2016.

A supporter of Democratic U.S. presidential candidate Bernie Sanders holds a sign as a video plays before the start of a campaign rally and concert at the University of Iowa in Iowa City, Iowa on January 30, 2016.

An ABC News crew sets up for a live broadcast in the rain Republican U.S. presidential candidate Ted Cruz speaks inside a hangar at the Webster City Municipal Airport in Webster City, Iowa on January 7, 2016.

Democratic U.S. presidential candidate Bernie Sanders and his wife Jane wave to the crowd after a campaign rally in Des Moines, Iowa the night before the Iowa caucuses on January 31, 2016.

Republican U.S. presidential candidate Ted Cruz bows his head as he speaks at a campaign stop at Dordt College in Sioux Center, Iowa on January 5, 2016.

A photo of Republican U.S. presidential candidate Donald Trump stands over the fence at the home of George Davey, a formerly registered independent turned Republican Trump supporter. Davey puts up signage every election at his home off Jordan Creek Parkway and Pommel Place in Des Moines, Iowa.

Republican U.S. presidential candidate Rick Santorum prays with members of his campaign staff during lunch between stops in Le Mars, Iowa on October 30, 2015.

A young woman takes a photo of the stage design after Republican U.S. presidential candidate Ted Cruz's event with Dr. James Dobson, an evangelical Christian author in Winterset Stage in Winterset, Iowa January 4, 2016.

A supporter of Republican U.S. presidential candidate Donald Trump reaches out for a handshake after a rally in Spencer, Iowa on December 5, 2015.

A member of Democratic U.S. presidential candidate Bernie Sanders' staff awaits his arrival as arrows point his path toward the microphone at an event in a garage in Charles City, Iowa on January 30, 2016.

U.S. Secret Service agents secure the area around the motorcade of Republican U.S. presidential candidate Ben Carson after a campaign even at South Bethel Church in Tipton, Iowa on November 22, 2015.

A flag waves in the wind outside a house down the street from where Democratic U.S. presidential candidate Bernie Sanders was scheduled to speak in Marshalltown, Iowa on January 31, 2016.

Democratic U.S. presidential candidate Maryland Governor Martin O'Malley listens to his introduction as he prepares to speak at the Des Moines County Democrats' fundraiser in Burlington, Iowa on November 7, 2015.

A man adjusts a flag ahead of Republican U.S. presidential candidate Ted Cruz' campaign stop at Godfather's Pizza in Spirit Lake, Iowa on January 6, 2016.

Attendees, including the local sheriff, mingle before Republican U.S. presidential candidate Marco Rubio's town hall event in Pella, Iowa on December 30, 2015.

Laurale Hunter rests her head on the chest of Republican U.S. presidential candidate Ben Carson after he gave a speech about his faith life at South Bethel Church in Tipton, Iowa on November 22, 2015.

Supporters listen as Republican U.S. presidential candidate Ted Cruz does a live television interview ahead of his campaign stop at Prime Time Restaurant in Guthrie Center, Iowa on January 4, 2016.

A member of the New Jersey State Police Executive Protection Unit watches over the crowd as Republican presidential candidate New Jersey Governor Chris Christie greets supporters after a town hall event at Mickey's Irish Pub in Waukee, Iowa on December 30, 2015.

Republican U.S. presidential candidate Ted Cruz does a live television interview with Sean Hannity before a campaign stop at Prime Time Restaurant in Guthrie Center, Iowa on January 4, 2016.

Supporters watch as Democratic U.S. presidential candidate Hillary Clinton speaks during a town hall at Old Brick Church in Iowa City, Iowa on December 16, 2015.

Republican U.S. presidential candidate Donald Trump turns to the crowd behind him during a campaign event in Des Moines, Iowa on Friday, Dec. 11, 2015.

Andy Meyer , Maggie Timboe, Sasha Fetty and Mia Tiric listen to Democratic U.S. presidential candidate Hillary Clinton speak on screen while at a debate watch event in support of Democratic U.S. presidential candidate Bernie Sanders in Des Moines, Iowa on November 14, 2015.

Democratic U.S. presidential candidate Hillary Clinton points to a question in the audience at a campaign event at Clinton Middle School in Clinton, Iowa on November 22, 2015.

Republican U.S. presidential candidate Donald Trump looks out into the crowd for his Iowa campaign manager while speaking press conference at the John Wayne Birthplace and Museum in Winterset, Iowa on January 19, 2016.

Republican presidential candidate Rick Santorum wades through the deep grass while participating in the Col. Bud Day Pheasant Hunt hosted by Congressman Steve King outside of Akron, Iowa on October 31, 2015.

Democratic U.S. presidential candidate Governor Martin O'Malley lunch after speaking at the Hardin County 2016 Chili Spectacular at the Iowa Falls American Legion in Iowa Falls, Iowa on January 10, 2016.

Debra Sage, a supporter of U.S. Republican presidential candidate Ted Cruz, from Grinnell, Iowa listens as Cruz speaks at a campaign stop at a Pizza Ranch restaurant in Newton, Iowa on November 29, 2015.

Protestors carry signs and chant before a campaign event for Republican U.S. presidential candidate Donald Trump at University of Northern Iowa in Cedar Falls, Iowa on January 12, 2016.

The U.S. Secret Service detail for Republican U.S. presidential candidate Donald Trump stands watch as he signs autographs at a campaign event at University of Northern Iowa in Cedar Falls, Iowa on January 12, 2016.

A woman photographs the podium before Democratic U.S. presidential candidate Bernie Sanders' speech a rally on caucus night in Des Moines, Iowa February 1, 2016.

Republican U.S. presidential candidate Donald Trump is seen on TV at the High Life Lounge in Des Moines, Iowa as he participates in the the Republican debate on FOX Business network in Columbia, South Carolina on January 14, 2016.

A supporter of Democratic U.S. presidential candidate Bernie Sanders holds a sign as a video plays before the start of a campaign rally and concert at the University of Iowa in Iowa City, Iowa on January 30, 2016.

An ABC News crew sets up for a live broadcast in the rain Republican U.S. presidential candidate Ted Cruz speaks inside a hangar at the Webster City Municipal Airport in Webster City, Iowa on January 7, 2016.

Democratic U.S. presidential candidate Bernie Sanders and his wife Jane wave to the crowd after a campaign rally in Des Moines, Iowa the night before the Iowa caucuses on January 31, 2016.

Republican U.S. presidential candidate Ted Cruz bows his head as he speaks at a campaign stop at Dordt College in Sioux Center, Iowa on January 5, 2016.

A photo of Republican U.S. presidential candidate Donald Trump stands over the fence at the home of George Davey, a formerly registered independent turned Republican Trump supporter. Davey puts up signage every election at his home off Jordan Creek Parkway and Pommel Place in Des Moines, Iowa.